1. Field of the Invention
This invention relates to a method for photographic processing a silver halide color photographic material, and, specifically, to a method for photographic processing a silver halide color photographic material which has sufficient bleach activity and can always afford a color image of good quality.
2. Description of the Prior Art
In the processing of a silver halide color photographic material, it is the usual practice to expose the photographic material imagewise, develop the exposed photographic material (the photographic silver halide emulsion may be fogged in advance) with a developer containing an aromatic primary amine developing agent in the presence of a color-forming coupler to obtain a color image, simultaneously re-halogenate the developed silver formed, and to remove it together with the undeveloped silver halide by fixation (or bleach-fixation).
Heretofore, potassium ferricyanide, ferric chloride and a ferric complex of aminopolycarboxylic acid have been the main bleaching agents used. The potassium ferricyanide and ferric chloride are good bleaching agents in that they have sufficiently high rates of bleaching (rates of oxidation) and can oxidize the developed silver sufficiently within a given period of time. However, because a bleaching bath containing potassium ferricyanide as a bleaching agent liberates a cyanide ion upon photolysis and causes environmental pollution, measures must be taken to render the spent bleach bath completely hazard free.
A bleaching bath containing ferric chloride as a bleaching agent has a very low pH and very high oxidizing power and tends to corrode the components of a processor in which the bleach bath is filled. Moreover, in a washing step after bleaching, iron hydroxide precipitates in the emulsion layer causing so-called stain. For this reason, the photographic material which has been subjected to the bleaching treatment must be washed with an organic chelating agent, which does not serve to speed processing or save energy. Furthermore, from the environmental viewpoint, there is the risk of the generation of hydrogen halide gas.
Metal complexes of organic acids such as a metal complex of an aminopolycarboxylic acid cause less environmental pollution than does potassium ferricyanide or ferric chloride, and these metal complexes have gained increasing acceptance as bleaching agents in recent years. Unfortunately, organic metal complexes generally have relatively low oxidizing power and insufficient bleaching power. A bleaching bath containing such a metal complex as a bleaching agent may produce the desired result when used to treat a silver halide color photographic material of low sensitivity composed mainly of a silver chlorobromide emulsion. However, it exhibits insufficient bleaching action on a silver halide color photographic material of high sensitivity composed mainly of a spectrally sensitized silver chlorobromoiodide or silver iodobromide emulsion, especially on a silver halide color photographic material containing an emulsion having a high silver content. As a result, removal of silver is poor, or the dye formed by oxidative coupling between the oxidation product of the color developing agent and the coupler remains as a leuco dye, which is the reaction intermediate, even after the bleaching step, and a dye cannot be completely formed (so-called poor color reproduction). The term "emulsion having a high silver content", as referred to herein, denotes an emulsion containing a total amount of silver in blue-sensitive, green-sensitive and red-sensitive silver halide emulsion layers of at least about 30 mg per 100 cm.sup.2.
Unless this problem is solved, it is impossible to achieve rapid processing of a high sensitivity silver halide color photographic material.
As one solution to the problem, U.S. Pat. No. 3,770,437 suggests the addition of a bromate to an iron complex of aminopolycarboxylic acid. It has been found, however, that immediately after formulation such a bleaching bath is suitable--the leuco dye product is converted to a dye. However, when the bleaching bath is allowed to stand after formulation, its oxidizing ability is rapidly reduced and the oxidation of the leuco product becomes insufficient. This is a fatal defect, which also occurs at the acidity (i.e., pH of 4 to 6) at which the bleaching bath is said to be relatively stable. Another defect is that magenta stain occurs.
In an attempt to remove this defect, Japanese Patent Application (OPI) No. 29719/78 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application") suggests the provision of a solution containing a bromate before the bleaching bath. However, since this increases the processing one step it is complicated and the processing time is prolonged.